Update readme and improve the documentation and examples

README.md

docs/fully_coherent_search_using_MCMC.md

docs/img/fully_coherent_corner.png

docs/img/fully_coherent_init_0_walkers.png

docs/img/fully_coherent_search_using_MCMC_corner.png

docs/img/fully_coherent_search_using_MCMC_walkers.png

docs/img/fully_coherent_walkers.png

docs/make_fake_data.md

docs/tuning_parameters.md

examples/fully_coherent_search_using_MCMC.py

examples/make_fake_data.py